Metallic iron is currently derived from magnetite, taconite and hematite ores. In the face of ever dwindling reserves of high grade magnetitic and taconitic ores, it is expected that greatly increased tonnages of hematitic ore will be recovered in the foreseeable future.
Presently, hematite is recovered from the siliceous, non-ferrous mineral matter in which it naturally occurs, through a process of selective flocculation wherein causticized starch is employed as the flocculant. The operation of this process is conducted under alkaline conditions, generally within the range of pH 9-11.5. Although corn starch is the most frequently employed flocculant, U.S. Pat. No. 3,292,780 issued Dec. 20, 1966, to Frommer et al. discloses a process employing tapioca flour as the selective flocculant. Employment of starches in the recovery process has, however, major drawbacks. From an ecological vantage point, the presence of residual starches in the waste water increases the biodegradeable oxygen demand and thereby creates a pollution problem in the disposal of the waste waters. From a commercial vantage point, there are an ever-increasing number of countries in which use of reagents having a food value, such as starch, is prohibited in commercial applications.
Accordingly, there exists the need for a process for recovering hematite from its gangue which at once both overcomes the deficiencies of the conventional process and reduces consumption of products having food value.